1. Field of the Invention
The present invention relates to a combination weighing apparatus equipped with a plurality of weighing hoppers.
2. Description of the Prior Art
The combination weighing apparatus generally includes a plurality of weighing hoppers and is designed to select one or a combination of those weighing hoppers so as to measure an intended or required weight of articles accommodated within such one or a combination of those weighing hoppers. This type of the combination weighing apparatus also includes, in addition to the weighing hoppers, a dispensing feeder and pooling hoppers. In such combination weighing apparatus, at the time of a setup operation in which the articles being handled are changed from one kind to another or at the time of cleansing, the articles remaining within the dispensing feeder, the pooling hoppers and the weighing hoppers have to be removed or discharged out of the system. Also, it often occurs that the weighing hoppers are cleansed when the necessity arises.
In such cases, each of the hoppers are kept open to allow removal or discharge of the articles by continuously supplying an electric power to electric motors each used to open the respective hoppers. If the hoppers are kept open for a substantial length of time, the motors tend to heat up, resulting in damages to the motors.
On the other hand, the combination weighing apparatus of the kind disclosed in the Japanese Laid-open Patent Publication No. 7-198465 employs a link mechanism for opening and closing hoppers so that while the link mechanism keeps the hoppers in a fully opened position, the supply of an electric power to the electric motors is interrupted so long as the hoppers are kept in the fully opened position. However, since according to the above mentioned publication the hoppers can be kept in the fully opened position by means of the link mechanism, the link mechanism is necessarily complicated. Because of this, not only is the cost of manufacture of the apparatus high, but the complicated link mechanism tends to be contaminated with articles and/or foreign matter, resulting in complications in cleansing.
In such case, it may be contemplated to use a predetermined trigger to close a gate of each of the hoppers. However, it may occur that all of the gates of those hoppers are closed at a time by a trigger signal, surprising an operator.
In view of the foregoing, the present invention is intended to provide a combination weighing apparatus wherein electric motors are hardly damaged and link mechanism will not be complicated.
Another important object of the present invention is to provide a combination weighing apparatus of the type referred to above wherein even when the gates are abruptly closed during the setup operation or the cleansing operation, the operator will not be taken aback.
In order to accomplish the foregoing objects of the present invention, there is provided in accordance with a first aspect of the present invention a combination weighing apparatus which includes a plurality of hoppers each having a gate and being capable of accommodating an article and discharging it therefrom upon opening of the respective gate; a drive device for selectively opening and closing the gate and maintaining the gate in an opened position when in a conducting state; and a control device for controlling the drive device and having a weighing mode, in which the gates of the hoppers selected for combination are opened to combine the respective articles, and a discharge mode in which the articles within the hoppers are discharged while the gates are maintained in the opened position.
In this combination weighing apparatus of the present invention, when during the discharge mode a condition of at least one of the drive device, an electric power supplying device for supplying an electric power to the drive device and the gate reaches a setting level, said control device drives the drive device to control the gate to close.
According to the present invention, since when the condition of at least one of the drive device, the electric power supplying device for supplying an electric power to the drive device and the gate attains the setting level the gate is closed, the drive device for maintaining the gate in the opened position is brought into a non-conducting state after a predetermined length of time. Accordingly, it is possible to avoid any possible damage resulting from heat-up of the motors.
In a first preferred embodiment of the present invention, the combination weighing apparatus also includes a detecting device for detecting a driving condition of the drive device when the gate is opened, so that when a detected value detected by the detecting device during the discharge mode attains a predetermined value, said control device drives the drive device to control the gate to close.
According to this first preferred embodiment, since when the detected value detected by the detecting device attains the predetermined value the gate is closed, the drive device for maintaining the gate in the opened position is brought into a non-conducting state after a predetermined length of time. Accordingly, it is possible to avoid any possible damage resulting from heat-up of the motor.
In a second preferred embodiment of the present invention, the detecting device is employed in the form of a timer so that when an opened condition of the gate lasts a predetermined length of time during the discharge mode, the control device controls the gate to close.
According to the second embodiment described above, since the gate is closed after the predetermined length of time, the drive device for maintaining the gate in the opened position is brought into the non-conductive state after the predetermined length of time. Accordingly, damages which may be brought about by heat-up of the motor can be prevented.
It is to be noted that since when the drive device is brought into the conductive state the gate is maintained in the opened position, there is no possibility that the link mechanism may be complicated.
In a third preferred embodiment of the present invention, when during the discharge mode in which the gate is in the opened position, the temperature of the electric power supplying device for maintaining the gate in the opened position as a result of the conduction attains a predetermined temperature, the control device controls the gate to close.
In the present invention, the term xe2x80x9celectric power supplying devicexe2x80x9d encompasses an electric power source circuit of the entire combination weighing apparatus and/or an electric power source circuit for motors used to selectively open and close the hoppers.
According to the third embodiment described above, since when the temperature of the electric power supplying device attains the predetermined temperature while the gate is in the fully opened position, the gate is closed, the drive device can be brought into a non-conductive state. Accordingly, as is the case with the first embodiment, damages which may be brought about by heat-up of the motor can be prevented.
In a fourth preferred embodiment of the present invention, when during the discharge mode in which the gate is in the opened position, a cumulative value of a driving current or an electric power of the electric power supplying device for maintaining the gate in the opened position as a result of the conduction attains a predetermined value, said control device controls the gate to close.
According to the fourth embodiment described above, since the gate is closed when the electric power or the driving current of the electric power supplying device attains the predetermined value with the drive device consequently brought into the non-conductive state, as is the case with the first embodiment damages which may be brought about by heat-up of the motor can be prevented.
n a preferred embodiment of the present invention, a sound source generates sounds upon the closing operation of the gate during the discharge mode, that is, before the closing operation of the gate and/or during the closing operation of the gate. This feature is advantageous in that since at the time of closure of the gate a precautious warning is available by means of sounds, an operator servicing the combination weighing apparatus can be informed beforehand or during the closing operation of the gate. Accordingly, the operator will not be taken aback at the time the gate is to be closed.
In another preferred embodiment of the present invention an average speed of closing of the gate during the discharge mode is controlled to a value lower than an average speed of closing of the gate during the weighing mode. Since the speed at which the gate is closed is low, the operator can quickly take necessary steps even when the gate is abruptly closed.
According to a second aspect of the present invention, there is provided a combination weighing apparatus which includes a plurality of hoppers each having a gate and accommodating an article and discharging it therefrom upon opening of the respective gate; a drive device for selectively opening and closing the gate and maintaining the gate in an opened position when in a conducting state; and a control device for controlling the drive device and having a weighing mode, in which the gates of the hoppers selected for combination are opened to combine the respective articles, and a discharge mode in which the articles within the hoppers are discharged while the gates are maintained in the opened position. In this combination weighing apparatus, the control device performs a control of setting a closing duration of the gate during the discharge mode to a value longer than a closing duration of the gate during the weighing mode.
According to this second aspect of the present invention, since during the discharge mode the closing duration in which the plural gates are closed all at a time is long, that is, the gates are closed at a low speed, it is possible to suppress the possibility of the operator being taken aback.
In a preferred embodiment of the present invention, during the discharge mode the gate is intermittently moved a number of times to cause the gate to undergo the closing operation, so that sounds can be generated each time the gate undergoes the intermittent movement. In other words, during the discharge mode in which the gate is undergoing the closing operation, by repeating an operation that discontinuously varies the speed of movement of the gate, the sounds can be generated each time the speed of movement of the gate varies discontinuously.
According to this feature, when the gate generates the sounds during closure of the gate, it is possible to suppress the possibility of the operator being taken aback which would otherwise occur when the gate closes abruptly.
In a further preferred embodiment of the present invention, the speed of movement of the gate being closed is chosen to be higher during the movement thereof than that at the time of termination of movement of the gate, so that the bigger sounds can be generated during the movement of the gate than at the time of termination of movement of the gate. According to this preferred embodiment, since the sound generated during the movement of the gate is big, not only can the closure of the gate be informed to the operator with no fault, but also unnecessary obnoxious sounds can be reduced since the volume of the sound generated at the time of termination of movement of the gate is small.
In a still further preferred embodiment of the present invention, the combination weighing apparatus further includes an input setting device for enabling at least one of driving parameters including a closing duration of the gate during the discharge mode, a speed of rotation of a drive source of the drive device and angle of rotation of the drive source to be inputted. According to this embodiment, inputting of the driving parameter allows the user to set the length of time and the volume of the sound to be generated at his or her will.
In such embodiment, the combination weighing apparatus preferably includes a select device for setting control patterns of at least two of a control of the gate closing duration by the control device during the discharge mode, a control of a speed of rotation of the drive source, a control of an angle of rotation of the drive source and a control of a speed of movement of the gate, and also for selecting one of the plural control patterns.